This disclosure relates generally to medical device delivery systems, and in particular, to a flared strain relief member disposed about a proximal end portion of an elongate sheath. More particularly, the disclosure relates to a flared strain relief member operatively coupled to a medical device delivery system that employs a unidirectional handle. These systems have a host of uses, including for example, the deployment of rapid insertion self-expanding devices such as stents, prosthetic valve devices, and other implantable articles inside a patient's body (individually and collectively, “stent” or “stents”). Exemplary embodiments of medical device delivery systems have been described in the U.S. Provisional Patent Application filed on Apr. 20, 2005 entitled, “Delivery System and Devices for the Rapid Insertion of Self-Expanding Devices” and having an application Ser. No. 60/673,199, and the non-provisional application filed on Apr. 20, 2006 by the same title and claiming the benefit of the filing date application Ser. No. 60/673,199 under 35 U.S.C. §119(e), the disclosures of which are incorporated in its entirety. The strain relief member may also be used, however, with balloon expandable and non-expanding stents. In addition to being used with a rapid insertion delivery system, the strain relief member may be used in an “over-the-wire” delivery system, so both systems will be described below.
By way of background, stents are configured to be implanted into body vessels having a passageway in order to reinforce, support, repair, or otherwise enhance the performance of the passageway. The term “passageway” is understood to be any lumen, channel, flow passage, duct, chamber, opening, bore, orifice, or cavity for the conveyance, regulation, flow, or movement of bodily fluids and/or gases of an animal. As an example, stents have been used in the passageways of an aorta, artery, bile duct, blood vessel, bronchiole, capillary, esophagus, fallopian tube, heart, intestine, trachea, ureter, urethra, vein, and other locations in a body (collectively, “vessel”) to name a few.
One type of stent is self-expanding. For a self-expanding stent, the stent is resiliently compressed into a collapsed first, smaller diameter, carried by the delivery system, and due to its construction and material properties, the stent expands to its second, larger diameter upon deployment. In its expanded configuration, the stent exhibits sufficient stiffness so that it will remain substantially expanded and exert a radially outward force in the vessel passageway on an interior surface of the vessel. One particularly useful self-expanding stent is the Z-stent, introduced by Cook Incorporated, due to its ease of manufacturing, high radial force, and self-expanding properties. Examples of the Z-stent are found in U.S. Pat. Nos. 4,580,568; 5,035,706; 5,282,824; 5,507,771; and 5,720,776, the disclosures of which are incorporated in their entirety. The Zilver stent is another particularly useful self-expanding stent is the Z-stent, introduced by Cook Incorporated, due to its nitinol platform and use of the Z-stent design properties. Examples of the Zilver stent are found in U.S. Pat. Nos. 6,743,252 and 6,299,635 by way of illustration and not by way of limitation, the disclosures of which are incorporated in their entirety.
Many delivery systems employ a tubular catheter, sheath, cannula, introducer, or other medical delivery device (individually and collectively, “catheter”) having first and second ends and comprising a lumen for receiving the wire guide. Optionally, these delivery systems may fit through a working channel within an endoscope or an external accessory channel device used with an endoscope.
Generally stated, these delivery systems may fall within two categories. The first category of delivery systems to have been used, and consequently the first to be discussed below, is commonly referred to as an “over-the-wire” system. The other category of delivery systems is sometimes referred to as a “rapid exchange” catheter. In either system, a wire guide is used to position the stent delivery system within a vessel passageway. The typical wire guide has proximal and distal ends. A physician inserts the distal end into the vessel passageway, advances, and maneuvers the wire guide until the distal end reaches its desired position within the vessel passageway.
In the “over-the-wire” catheter delivery system, a physician places the catheter over the wire guide, with the wire guide being received into a lumen that extends substantially through the entire length of the catheter. In this over-the-wire type of delivery system, the wire guide may be back-loaded or front-loaded into the catheter. In front-loading an over-the-wire catheter delivery system, the physician inserts the distal end of the wire guide into the catheter's lumen at or near the catheter's proximal end. In back-loading an over-the-wire catheter delivery system, the physician inserts a distal portion of the catheter over the proximal end of the wire guide. The back-loading technique is more common when the physician has already placed the wire guide into the patient, which is typically the case today. In either case of back-loading or front-loading an over-the-wire catheter delivery system, the proximal and distal portions of the catheter will generally envelop the length of the wire guide that lies between the catheter first and second ends. While the wire guide is held stationary, the physician may maneuver the catheter through the vessel passageway to a target site at which the physician is performing or intends to perform a treatment, diagnostic, or other medical procedure.
Unlike the over-the-wire system where the wire guide lies within the catheter lumen and extends substantially the entire length of the catheter, in a “rapid exchange” catheter delivery system the wire guide occupies a catheter lumen extending only through a distal segment of the catheter. The so-called rapid exchange system comprises a system proximal portion, an elongate flexible middle section delivery device, and a system distal portion that is generally tubular.
The system distal portion, in general, comprises an inner guide channel member sized to fit slidably within an outer guide channel member that is substantially axially slideable relative to the inner member. The outer guide channel member and inner guide channel member further have entry and exit ports defining channels configured to receive a wire guide. A port includes any structure that functions as a portal, port, passage, passageway, opening, hole, cutout, orifice, or aperture, while a guide channel is understood to be any passageway, lumen, channel, flow passage, duct, chamber, opening, bore, orifice, aperture, or cavity that facilitates the passage, conveyance, ventilation, flow, movement, blockage, evacuation, or regulation of fluids or gases or the passage of a diagnostic, monitoring, scope, other instrument, or more particularly a catheter or wire guide.
A wire guide may extend from the outer and inner member entry ports, through the outer and inner member guide channels, and exit the system distal portion at or near a breech position opening located at or near a transition region where the guide channels and exit ports are approximately aligned relatively coaxially to facilitate a smooth transition of the wire guide. Furthermore, the outer guide channel member has a slightly stepped profile, whereby the outer guide channel member comprises a first outer diameter and a second smaller outer diameter proximal to the first outer diameter and located at or near the transition region.
The system distal portion also has a self-expanding deployment device mounting region (e.g., a stent mounting region) positioned intermediate the inner guide channel member entry and exit ports for releasably securing a stent. At the stent mounting region, a stent is releasably positioned axially intermediate distal and proximal restraint markers and sandwiched transversely (i.e., compressed) between the outside surface of the inner guide channel member and the inside surface of an outer guide channel member.
Turning to the system proximal portion of the rapid exchange delivery system, the system proximal portion, in general, comprises a handle portion. The handle portion has a handle that the physician grips and a pusher stylet that passes through the handle. The pusher stylet is in communication with—directly or indirectly through intervening parts—the inner guide channel member at the distal end. Meanwhile, the handle is in communication with—directly or indirectly through intervening parts—the outer guide channel member at the system distal portion. Holding the pusher stylet relatively stationary (while, for example, actuating the handle) keeps the stent mounting region of the inner guide channel member properly positioned at the desired deployment site. At the same time, proximally retracting the handle results in a corresponding proximal movement of the outer guide channel member relative to the inner guide channel member to thereby expose and, ultimately, deploy the self-expanding stent from the stent mounting region. At times, a physician may need to deploy a second self-expanding stent by withdrawing the system from the proximal end of the wire guide. The physician may then reload the catheter with additional stents, and if that is not an option the physician may load another stent delivery system with an additional stent, onto the wire guide. Also, the physician may withdraw the stent delivery system altogether and replace the delivery system with a catheter or different medical device intended to be loaded onto the wire guide.
The delivery system in the rapid exchange delivery system further comprises an elongate flexible middle section delivery device extending intermediate the system proximal portion and the system distal portion. The middle section delivery device comprises an outer sheath and an inner compression member having a first end and a second end portion associated with the system distal portion and system proximal portion, respectively.
More particularly, an outer sheath first end portion may be coterminous with or, if separate from, may be associated with (e.g., joined or connected directly or indirectly) the system distal portion outer guide channel member at or near the transition region, while the outer sheath second end portion is associated with the handle at the proximal end. The inner compression member first end portion is associated with the system distal portion inner guide channel member at or near the transition region, while the inner compression member second end is associated with the pusher stylet at the proximal end. Therefore, the outer guide channel member of the system distal portion may move axially (as described above) and independently relative to an approximately stationary inner guide channel member of the system distal portion and, thereby, deploy the stent.
A challenge in designing the system proximal portion of a delivery system in the rapid exchange delivery system is that the system proximal portion of a catheter for use with the system typically has a small outer diameter that does not mate properly to the handle. The handle could be reconfigured to the smaller physical dimensions of the catheter, but this requires retooling the handle and thereby increasing the manufacturing cost of the delivery system.
Another problem is that the delivery system is continually pulled, twisted, and flexed such that the outer catheter proximal end portion and the handle experience a great deal of force as the delivery system negotiates a tortuous path within a vessel passageway and pulls the outer sheath and/or other stent-covering catheter proximally over the stent in order to expose and thereby to deploy the stent during the medical procedure. Conventional methods of joining strain relief in medical devices may be to use purely mechanical connectors such as lap joints, nuts, pins, screws, clamps, and bushings. Given the small physical dimensions of the catheter and the strain relief, mechanical connectors increase the difficulty in manufacturability and, therefore, the assembly time. Another drawback to a mechanical connector is the propensity to lose the friction fit between the components. Accordingly, a glued joint is often employed as an alternative to a mechanical connector in medical devices. While glue, adhesives, and the like (collectively, “glue”), offer advantages over a mechanical connectors, one must choose the right glue to join dissimilar materials. Also, glue must cure, thereby increasing the total processing (fixture) time in the application and assembly of a joint. In any event, mechanical connectors and glue may vary in strength and integrity depending on the type of materials being joined, and whether the materials have incongruous mating surfaces.
Still another problem in conventional strain relief having a substantially uniform outer diameter is that the attachment point between the strain relief and the handle could dislodge, loosen, or fail due to inadequate stress distribution. When the connection between the strain relief and the handle fails totally or even in part, fluid leakage may result during flushing of the medical device, bodily fluid may leak by a capillary effect, or an air embolism might result. Thus, an improved seal is needed between the strain relief and the handle.
Therefore, it would be desirable to have a strain relief member that solves the aforementioned problems for use in medical device delivery systems such as, for example, a delivery system for deploying an implantable prosthesis (e.g., a self-expanding, balloon expandable, or non-expanding stent; prosthetic valve devices, and other implantable articles) at a selected location inside a patient's body, as taught herein.